Folding of sheet-material blanks

ABSTRACT

A sheet-material blank is advanced in a path and from laterally of the path a folding member is advanced slowly towards and into engagement with the blank, whereupon it is accelerated beyond the path to the other side thereof. The deflecting member is then withdrawn and the deflected portions of the blank are engaged between two rollers which rotate in mutually opposite directions and the blank is thereby folded by engagement with these rollers through the nip of which it passes.

This is a division, of application Ser. No. 301,603, fled Oct. 27, 1972,now U.S. Pat. No. 3,904,187.

BACKGROUND OF THE INVENTION

The present invention relates to the folding of sheet-material blanksand more particularly to a method and an apparatus for effecting suchfolding.

Sheet-material blanks must frequently be folded, for instance to form asignature in a book, brochure or the like. Such folding is ususallycarried out by means of a longitudinal or transverse folding deviceassociated with so-called rotary folders of the type used in variousrotary printing machines which use sheet material. As a rule, thesefolding devices use a conically or analogously convergent guide in whichthe sheet material blank is made to advance whereby it becomesprogressively folded. Another approach known from the art is to usetransverse folding cylinders. In some instances, where the fold must becarried out with particular accuracy, so-called knife-folders areemployed. These "knives" are folding elements which are guided toperform a movement during which they engage the respective sheetmaterial blank and fold it. It is known to guide the knife in astraight-line guide or to articulate it to a swingable arm.

The problem with these latter types of folders is the drive for themovement which is to be performed by the knife, particularly if theknife is required to form a fold on a large-format sheet-material blank.This means that the knife must pass through a relatively significantstroke, and of course in modern equipment the high-speed operation ofthe machines necessitates that the number of strokes be correspondinglygreat. This means that a cam control of the knife movement, theinherently ideal way of controlling the movement, is no longer possible.It has already been attempted to effect the control by means ofelectromagnetic units. These last two types of drive arrangements havethe disadvantage that the number of strokes which is required in modernmachines per unit of time, cannot be achieved. Moreover, the drivesaccelerate the knife or deflecting element in such a manner that itengages the respective sheet-material blank in shock-like manner, adisadvantage in terms of the accuracy of folding which can be obtained.

Some improvement was obtained in this field by using straight-linearticulated crank linkages. Such crank linkages are driven and theoutput member of the linkage is associated with the knife which it thenmoves in a straight line. The difficulty with these arrangements is thatthe speed of movement of the last element, that is here the knife,decreases significantly long before the knife reaches the end of itsworking stroke. This means that that the sheet-material blank engaged bythe knife receives only a relatively brief but very strong impulsedeflecting it out of the path in which it travels, but is not positivelyguided subsequently because of the progressive retardation in the speedof advancement of the knife. Thus, the deflected portions of thesheet-material blank will slide more or less freely under the impulseinitially imparted to them by the knife, in the direction in which theyhave been deflected by the knife, before they are engaged by the foldingrollers which then complete the folding operation. In many instances,however, the sheet-material blanks have already previously been foldedby means of conical folding guides or other devices, so that they are ofV-shaped configuration, that is they are already bi-folded in onedirection. This means that at the opposite sides of the sheet-materialblank, that is at the opposite lateral edges thereof, differentstiffness and friction coefficients exist. This, in turn, means that assoon as the blank is no longer positively guided by contact with theknife, it will tend to shift its configuration and position anddepending upon the mass and the speed of the initial impulse imparted toit, it will reach the folding rollers at some angle of inclination.This, as is well known to thse conversant with the art, results invarious types of difficulties.

SUMMARY OF THE INVENTION

It is, accordingly, an object of the present invention to avoid thedisadvantages of the prior art.

More particularly it is an object of the present invention to provide animproved folding apparatus for folding of sheet-material blanks, whichis not possessed of the aforementioned disadvantages.

Another object of the invention is to provide an improved method ofeffecting the folding of sheet-material blanks.

In pursuance of these objects, and of others which will become apparentherefter, one feature of the invention resides in guiding asheet-material blank in a predetermined path, and advancing a deflectingelement (e.g. a folding knife) at relatively slow speed from one side ofthe path toward and into engagement with the blank. Thereupon, thedeflecting element is accelerated and simultaneously advanced togetherwith portions of the blank out of the path and to the opposite side ofthe latter, where such portions can be engaged by the folding rollers.According to the invention the acceleration of the deflecting elementassures that it will always be in positive guiding engagement with thedeflected portions of the sheet-material blank so that the disadvantagesof the prior art cannot occur.

The apparatus for carrying out the novel method is capable of producingat high speed and can therefore be employed to economic advantage. Theinvention is applicable both to transverse folders and to longitudinalfolders, that is apparatuses which effect transverse or longitudinalfolding of sheet material blank. It assures that the deflecting elementengages the sheet-material blank at low speed, rather than to impart astrong impulse thereto. Once the blank has been engaged, the deflectingelement is accelerated together with the blank and the latter is thusbeing positively guided by continued engagement with the deflectingelement until the deflected portions of the sheet-material blank havereached a position in which they can be engaged by the folding rollers.

According to a currently preferred embodiment of the invention weutilize an articulated crank linkage which drives the deflecting elementin a straight-line path, and whose movemment is in turn controlled byso-called anti-parallel crank linkages. The output member of theanti-parallel crank linkage is at one and the same time also the inputmember of the straight-line crank linkage arrangement. However, it isalso possible to use, in place of the anti-parallel crank linkages,elliptically configurated wheels.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the acompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a somewhat diagrammatic side view illustrating one embodimentof the invention;

FIG. 2 is a graph comparing the characteristics of movement of thedeflecting element in an apparatus according to the present inventionand in accordance with the prior art; and

FIG. 3 is analogous to FIG. 1 but illustrating a further embodiment ofthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Discussing firstly the embodiment in FIG. 1 it will be seen thatreference numeral 1 designates a somewhat diagrammatically illustratedrotatable drive shaft 1 which drives a crank 2 which, together with acoupling element 3, a crank 4 and a fixed element 5 constitutes acounter-motion anti-parallel crank drive in which during rotation of thecrank 2 in one direction the crank 4 connected thereto by the couplingelement 3 rotates in the opposite direction of rotational speedsdifferent from those of the crank 2. In accordance with the presentinvention the crank 4 is the output element of the anti-parallel crankdrive, but at the same time is also the input or drive crank of thestraight-line crank linkage arrangement which, in addition to the crank4, has the coupling element 6, the glide rod 7 which carries at itsfront the deflecting element 9, and the straight-line guide 8.

Reference numeral 11 identifies a guide having the illustrated slotwhich registers with the nip 14 and find between two folding rollers 13and 12 which rotate in mutually opposite directions as illustrated bythe associated arrows. The sheet-material blanks 10, of which one isshown, advance on this guide 11 in a predetermined path, defined by thesurface of the guide 11 which faces upwardly in FIG. 1. They move acrossthe gap in the guide 11 and it will be understood that they havepreviously been severed from endless webs of sheet material, that theymay have been printed or otherwise processed, that they may have beenfolded longitudinally and/or transversely and that there may be morethan one of these blanks 10 provided on the guide 11 in overlyingrelationship. In other words, it is possible to fold two or more of theblanks 10 simultaneously.

It is clear that when the element 9 moves from one side of the path (theupper side in FIG. 1) across the path to the other side (the lower sidein FIG. 1), it deflects the blank 10 as illustrated through the slot inthe guide 11. Depending upon the length of the stroke required to beperformed by the element 9, the coupling element 6 may be pivoted at apivot 15 or if maxiumum stroke length is required, at the pivot 16 whichin any case exists and connects the coupling element 3 with the crank 4.It is also possible, however, to provide an arrangement in which thepivot 15 can be shifted on the crank 4 in order to permit the strokelength to be varied if and as required.

If the arrangement uses only a single straight-line crank linkagearrangement, for instance that illustrated in FIG. 1 and comprising thecrank 4, the coupling element 6, the rod 7 and the guide 8, as is knownfrom the prior art, then the element 9 will be undergoing onlyinsignificant acceleration at the time it contacts the blank 10 at pointA₁ (see FIG. 2), as indicated by the solid line in FIG. 2, Theacceleration which the element 9 has at the time it contacts the blank10 at point A₁, is maintained over only a short period S₁ until thepoint E₁ is reached. FIG. 2 shows clearly that the speed of the element9 decreases quite rapidly in the direction towards the point E₁, so thatthe deflected blank 10 is no longer being positively guided byengagement with the element 9 and will be able to move relatively freely(without guidance) in the direction towards the nip 14 (FIG. 1).

Relatively expensive attempts have been made to overcome this problem inthe art, for instance to retard the blank 10 by brake or frictionrollers located above the guide 11, so as to prevent the free movementof the deflected portions of the blank, that is movement which iscontinued at the initial speed of deflection whereas the element 9 isprogressively retarded. Even this, however, has been of no help in theprior art and especially due to the fact that the blanks 10 have usuallyalready been previously folded one or more times, the problems occurwhich have been outlined above, as soon as the non-positively guidedblank is then engaged by rollers 12 and 13.

The present invention, however, avoids these difficulties. FIG. 2 showsthat during the working stroke of the element 9 there is obtained adistance-speed relationship as is indicated by the broken line 21 inFIG. 2. It will be noted that the element 9 engages the blank 10 atpoint A₂ with relatively low speed and that it then accelerates theblank increasingly until it extends substantially beyond the guide 11;the acceleration of the element 9 and consequently of the blank 10 isterminated only when the nip 14 has almost been reached, that is it isterminated almost at point E₂ where the working stroke of the element 9ends. This means that the difficulties inherent in the prior art havebeen avoided, because any undesired displacement of the blank 10 is nolonger possible because it has already been engaged by the rollers 13and 14 and is positively guided by them.

If, in accordance with the prior art, only a straight-line crank linkagedrive is utilized, guidance of the blanks 10 can be effected only in theregion s₁ of FIG. 2, that is between the point of contact A₁ which isreached at almost maximum speed and the point E₁. In contradistinctionthereto, the present invention makes it possible to positively guide theblank 10 over a substantially longer distance s₂, extending between thecontact point A₂ which is reached at relatively low speed of the element9, and the point E₂ which is almost coincident with the end of theworking stroke of the element 9. This means that at identical angularspeed of the respective crank drive and at better utilization of theoperating rhythm, an improvement of the folded blanks, that is thequality of the folds thereof, is obtained with the present invention.This is obtained by having the movement of the element 9, and thereforethe deflection of the blank 10, be continuous in accordance with thepresent invention and by guiding the blank 10 positively from the momentit is deflected out of its path until it is engaged by the rollers 12and 13 at the nip 14 thereof.

In FIG. 3 we have illustrated a further embodiment of the invention.Like reference numerals identify the same components as in the emodimentof FIG. 1. Here, however, we have illustrated that in place of theanti-parallel cranks 2-5 it is possible to mount on the drive shaft 1 anelliptical wheel 17 which cooperates with an elliptical wheel 19 ofidentical size and which is mounted for rotation on a shaft 18. Thespacing of the axis of the shaft 18 from the axis of the shaft 1corresponds to the distance of the fixed points of articulation of themember 5 of the embodiment in FIG. 1. The coupling member 6 would thenhave to be articulated on the large elliptical axis of the wheel 19. Thedata given in FIG. 2 with respect to the operation of the embodiment ofFIG. 1, and the comparison with the prior art which is provided in FIG.2, hold identically true with respect to the embodiment of FIG. 3.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in anapparatus for folding sheet-material blanks, it is not intended to belimited to the details shown, since various modifications and structuralchanges may be made without departing in any way from the spirit of thepresent invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. In an apparatus for folding sheetmaterial blanks, a combination comprising guide means for guiding sheetmaterial blanks, substantially in a plane; a deflecting element guidedfor straight-line movement in a direction transversely of said planefrom a starting position in which it is located in its entirety at oneside of said plane to an operating position in which it extends with aportion thereof across said plane to the other side of the latter,whereby to engage and in part deflect the blank in said direction; andmotion-imparting means for imparting motion to said element in such amanner that the element moves from said starting position to said planeand travels at relatively slow speed when reaching sheet materiallocated in said plane and upon reaching said sheet material isaccelerated to a relatively higher speed while travelling from saidplane toward said operating position, said motion-imparting meanscomprising an anti-parallel crank linkage mounted at said one side ofsaid plane and including a fixedly mounted and rotatable drive shaftwhich is spaced from said element laterally of said plane, a first cranklink having a free first end and a second end which is connected to saiddrive shaft for turning with the same, a second crank link also having afree first end and a second end which is pivotally mounted at a fixedlocation which is spaced from said drive shaft in direction towards saidplane, a coupling element having spaced ends each of which is pivoted toa different one of said first ends, and a motion-transmitting elementhaving opposite end portions which are pivoted to said first end of saidsecond crank link and to said element, respectively, so that, inresponse to rotation of said drive shaft, said crank links pivot inmutually opposite directions and impart motion to said element in saidmanner.
 2. A combination as defined in claim 1, wherein said cranklinkage further comprises an elongated stationary member having one endportion at said drive shaft and another end portion to which said secondend of said second crank link is pivotally mounted at said fixedlocation.
 3. A combination as defined in claim 1; and further comprisinga pair of transversely spaced folding rollers mounted at said other sideof said plane for rotation in opposite directions about axes extendingsubstantially parallel to said plane, said folding rollers definingbetween themselves a gap which is aligned in said direction with saiddeflecting element so that the part of said blank that is deflected bysaid deflecting element enters said gap.
 4. A combination as defined inclaim 3, wherein said guide means comprises a guide support having aslot which registers in said direction with said deflecting element andsaid gap, respectively.
 5. A combination as defined in claim 1; andfurther comprising an elongated guide element mounted at said one sideof said plane and guiding said deflecting element for said straight-linemovement thereof.
 6. A combination as defined in claim 1, wherein saidcoupling element has a length which is greater than the length of saidfirst and second crank links, respectively.